Method and means for producing tightfitting patches for use in plywoodpatching machines



Feb. 13, 1962 P. o. SKOOG 3,021,249

METHOD AND MEANS FOR PRODUCING TIGHT-FITTING PATCHES FOR USE INPLYWOOD-PATCHING MACHINES Filed April 30, 1957 2 Sheets-Sheet 1 FIG PEROLOF SKOOG INVENTOR.

Feb. 13, 1962 P. o. SKOOG 3,021,249

METHOD AND MEANS FOR PRODUCING TIGHT-FITTING PATCHES FOR USE INPLYWOOD-PATCI-IING MACHINES Filed April 30, 1957 2 Sheets-Sheet 2 PEROLOF SKOOG IN VEN TOR.

Unite tats 3,021,249 METHOD MEANS FOR PRODUCING THGHT- FITTING PATCHESFUR USE IN PLYWODD- PATCHING MACHINES Per Olaf Skoog, Rte. 1, Box 290,Olympia, Wash. Filed Apr. 30, 1957, Ser. No. 656,096 6 Claims. (Cl.156-293) My present invention relates to the general art of patchmgplywood, and more particularly to a method and means for cutting, insequenial operation, a patch which will be a tight fit in the patchopening cut in the veneer sheet during the same operational sequence.

In the patching of plywood it is necessary to use machinery that willsequentially cut out the defective portion, thus leaving an opening inthe veneer sheet, and then to cut from another piece of veneer a patchto fit the opening just produced. In past operations it has beenobserved that, with sharp angles on the die-cutting edges of the veneerpatching machine, the plug or patch cut on the lower edge of the tabledie and the hole cut by the holepunch on the upper edge of the table diewere very nearly the same size. This clearance was of necessity so closethat the patch would not fit sufficiently tight in the sheet of veneerto prevent glue leakage into the joint when the sheets were laminatedinto plywood.

Experienced operators have found that it was necessary to hone theinside lower edge of the table die so as to cause it to cut a patchlarger than the actual opening in the table die. This arrangement givessufficient interference to prevent most leakage of the glue through thejoint after the plug is inserted into the sheet. To accomplish thiseffect, it is necessary to hold a hone on the lower cutting edge atabout 10 to with respect to the inside surface and honing the opening ofthe die so that the plug would be wider than the actual through dieopening. More honing was done where the patch was widest and less honingwhere the patch was narrow. This method could be made to work quitewell, except for certain limitations which will be further explained.

The honing operation is of necessity a hand operation, and it willtherefore depend upon the skill of a workman to achieve the properwidening of the die. It is dificult to tell by looking at the die whensufiicient honing has been achieved, and it was therefore found that thehoning could be best done when the die was installed on the patchingmachine. Under these conditions a patch could be cut and checked and, ifmore honing was required, it could be done on the machine. If the diewas overwidened by honing, the patch, being too large, would split theveneer sheet. Each time the die was resharpened the previous tightenedbevel was ground away and the die then required inside honing again. Ona machine of this type, used to patch plywood sheets, die sharpeningmust be done every day, and it can be seen that a highly skilledmechanic and considerable of his and the patching machines time wererequired when employing this method.

In this new method, the patch is tightened by reshaping the insidesurface of the die, by a stepped-back perpendicular wall, so that thepatch is tightened in the proper places. Furthermore, the surface isthus so cut that the sharpening of the lower cutting edge of the diedoes not change the size of the patch cut, and the die will continue tocut the same size patch until the lower cutting edge bearing portion isentirely ground away. Following this method, there is a taper from thisstepped-back surface to the standard die opening, and the purpose ofthis is to compress the plug so that it may enter the hole in the sheet,which is the same size in the upper opening in the table die. The sizeof the plug punch remains the same, as it is a standard set of dies,then it may pass clear through the table die and insert the patch in theseat. This method has overcome the many difficulties encountered in thepast with the various forms of honing which were resorted to, becausewith this method the die cuts the patch wider in proportion to the widthof the opening and maintains square edges. This feature is deemednecessary because wood is more compressible when stressed perpendicularto the grain than when out with the grain. The cross-grain dimensiontherefore is normally considered to be the width of the patch and withthe grain dimension is normally referred to as the length of the patcheven though the patch may be round, square or elongated.

The principal objects of my present invention, there-' fore, are toprovide a method and means so that in a sequential operation, where adefect is cut out of a piece of veneer, a replacement plug is cut whichwill be slightly larger than the opening provided and to insert thenewly cut plug into the defect opening so tightly that high gradeplywood can be made up from veneer sheets that have been so patched.

A further object of this present invention is to provide a veneerpatch-cutting die wherein the cutting edge will cut a veneer patch whichthen progresses through the die and in so doing passes through arestricting taper portion and then through a perpendicularly walledportion of the die which retains the compression imparted by the taperportion and holds it compressed until the moment that it is seated inthe defect opening previously cut.

A further object of this invention is to provide a die means in whichthe cutting portion of the die is provided with perpendicular innerwalls so that repeated honings can be made on the outer tapered surfaceof the cutting die, in order to maintain the keen cutting edge required,without in any way changing the inside dimensions of the die, and thisenables the die to continue to cut patches of a predetermined sizethroughout its entire working life.

A further object of this invention is to provide a method for cuttingveneer patches, in which during the cutting operation the wood isstressed perpendicular to the grain in order to take advantage of thefact that wood is more compressible under this condition than whenstressed with the grain.

Further objects, advantages and capabilities will be apparent from thedescription and disclosure in the drawings, or may be comprehended orare inherent in the device.

In the drawings:

FIGURE 1 is a vertical sectional view, in fragmentary form, showing thevarious elements involved in a sequential patching machine for plywood.

FIGURE 2 is a top plan view of a table die used in the arrangement ofFIGURE 1.

FIGURE 3 is an elevation of the die shown in FIG- URE 2.

FIGURES 4, S and 6 are enlarged vertical sectional views taken alongsimilarly numbered lines of FIG- URE 2.

FIGURE 7 is a diagrammatic view showing how the actual tightening grindis achieved by shifting the die-half toward the generating center andillustrating the values used in the formula devised for determining theamount of the tightening grind.

FIGURE 8 illustrates a variant form of die opening.

Referring more particularly to the disclosure in the drawings, thenumeral 10 designates the sheet of veneer to be patched. This sheet, inthe area immediately under consideration, is held down by the hold-down12 snugly against the table die 14 having the upper cutting edge 13 andthe lower cutting knife edge 50 which is fixed in position. In thesequential operation of patching a piece of veneer stock, the firstoperation is to grip sheet 10, as indicated in FIGURE 1, between thetable die 14 by means of the movable hold-down .12. Then thehole-cutting punch die 16 is driven downwardly through hold-down 12,which is provided with ample clearance at 18, so as to hold the'veneersecurely in place yet permit free passage of the knife type hole-punchdie 16. After cutting the opening at 20 in the veneer sheet 10, thehole-punch die 16 is retracted and, when well above the veneer sheet,the knockout punch 22 is driven downwardly as viewed with respect to die16, so as to knock out the cut veener waste piecewhichis disposed of invarious ways, leaving opening 20 clear. During part of this cycle theplug or patch punch 24 is being driven upwardly and cuts the veneerpatch 26 from aseparate sheet or strip of veneer, and *this'patch iscarried upwardly through die 14 by the plug punch until it is seated inopening 20 and substantiallyflush with thesurfaces of sheet 10.

In FIGURES 2 and 3 is shown the table die 14. This die, for convenienceof construction and as an economy in replacements, which may result fromdamage and the like, is preferably made of two separate pieces, as thehalfmembers 30 and 32. These members are each provided withthrough-securing bolt openings 34. Each of members 30 and 32 is machinedto provide one-half of the die outoutyas 36 and 37, respectively. Apreferred form of this'cutout is'after the showing of FIGURE 2. However,this present method may be'applied to variously shaped dies, such'asround, square, diamond shaped or any other desired-shape, and a variantform of this opening is shown in FIGURE 8, in which the general form isthe same as that shown in FIGURE 2, excepting that ateach end arcuateportions as 40 and Marc provided, which merge with the main wallportions as 44 and 46. The underside of die 14 conforms to the generalshowing of FIGURE 3, inwhich the walls of opening 35, as 36 and 37, arecontinued downwardly past the bolting-on flange portion 48, so as toprovide the cutting edge 50. A desirable characteristic of this cuttingedge is that the inner walls are perpendicularly disposed to the veneeras a cut is being made, and the outer walls 52 and 53 are tapered soas-to come to an apex with walls 36 and 37 and thus provide the taperingcutting edge 50 which is sharpened or honed on its outer surface only.

The form of the interior walls of table die '14 is very essential to thepresent invention and makes the present method possible. This form isprobably best shown in FIGURES '4, 5 and 6 which are vertical sectionstaken along'similarly numbered lines of FIGURE 2. It is to be noted thatthe upper portion of wall 36 is disposed at right angles to the uppersurface of the table die member '30. This is a desirable arrangement, asthe upper portion o'flhedie opening must accommodate the hole-punch die16 at-the lower portion of its cutting stroke, wherein the defect isbeing cut out of the veneer sheet 10. The lower portionof theinteriorwalls 36 and 37 is cut on a radius whose center of generation isshifted to the right as viewed in' FIGURE 7, the'amount of enlargementbeing indicated by the reference character t and is the increment 55. '1he new wall portion 56 is also disposed at right angles to the uppersurfaceof the die 14. The two parallel walls 56 and 36 are joined by atapered wall 58, said wall adapted to act as a forcing cone. Aconvenient taper for this wall is, as indicated in the drawings, 1.

Now,the extreme cutting edge 50 must be sharpened to a keen cuttingedge, and this can only be done under service conditions by honing thesame. It will be clear, it is' believed, from the'showing of FIGURES 4,5 and 6 that this honing need only be done on the outer surface as 52and 53, where it-can be'easily and uniformly accomplished. 'It is notnecessary to hone the inside of the die opening, because wall 56 issetback. from the vertical projection of'wall '3'6 by-the increment z, andthis is a fixed vertical wall throughout the life of the die and pro-VidCS filliIhfl'OVClSiZB cutting for patches .26 that will be requiredduring the life of the die. This is a marked im-r provernent over theolder methods, wherein the inside of a die opening was honed daily,normally, in order to achieve a cutting edge that would be outwardlydisposed sufficiently to make the patches somewhat oversize. This wasalways a hand operation and would vary with the individual, and theremight be a great variance between two individuals who at different timesmight work on the same die. The difficulty of leaving this operation tothe skill of a mechanic is due to the fact that the required clearancemay be only of the order ofthree to fiveor six-thousandths in normaloperations and normally within the extremes of one-thousandth of an.inchto seven-thousandths of an inch. The actual amount depends upon thethickness of the veneer and the species ofthe wood .forming the veneersto be patched.

As a die of this order is daily sharpened and sometimes more frequentlyhoned,rthere is considerable wear, and this has been indicated in FIGURE5 by the dotted line 60. It is believed it will be evident that, eventhough the entire cutting point was sharpened or honed away up to apoint where the cutting edge was at 62, as long as there is sulficientsurface 56 left to determine the margins of the patch, the patches willbe of the same peripheral form and size as those made when the die wasnewly installed with its cutting point out as indicated at 50.

My present method is believed to be quite in step with modern industrialrequirements, namely, that there should be a very minimum of stoppage ofany machine used in an industrial operation during its normal workinghours. It should be apparent, of course, that a number of men arerequired in the handling of materials to and from the patchingmachinery, and, if the machine does not satisfactorily perform and mustbe shut down, a very considerable and expensive wastage of personneltime ensues. With my present method and themeans to implement thesame,it is believed that the operational procedure of finishing andmaintaining dies of this order has been reduced to the exactness thatcan only he achieved by machine-finished operations. It for this reasonthat the oversize increment t is so much better established by anaccurate and precise machine operation than by hand honing, as has beenrequired in the past.

Extended trials and experiments have indicated that portions of the dierequire a larger offset than others, and this has been graphicallyrepresented 'in FIGURES 4, 5 and 6, in which FIGURE '4, taken along theminor or transverse axis of opening 35, takes the greatest amount ofoffset .or it. An average value for this offset is in the neighborohoodof .003 inch. The other extreme will be at the very end of the opening,or rather at the end of the longitudinal or greater axis, and at thispoint there will be little, if any, requirement for offset. For allpractical purposes, in the form shown in FIGURE 2 the die would beformed with the wall perfectly straight, as indicated in FIGURE 6. Atintermediate portions betweensections 44 and 66 as, for instance, thatindicated by section 5-5, an intermediate value would be employed whichwould be less than the value established along the minor'axis shown insection 4--4, the increment t varying from maximum at section 44 to aminimum, or zero for many forms of dies, at section 6--6. In the variantform of die illustrated in FIGURE 8, the maximum value for t would occuralong the minor or transverse axis and, as the curve of the end portionsindicated at 40 and 42 decreases in radius, there will he need fordecreasing the offset t for these portions.

FIGURE 7 illustrates *an application of the formula:

Substituting in this formula an oifset value of .010'inch for E, aradius B of 2.625 inches and a value of 1.78125 inches for C, then wearrive at a solution for t of .0032 inch. The actual radius D of circleB does not need to be known, in the machine operation of making thetightening grind, because the proper value is reached when circle Aintersects circle B at points 0, as the actual die-tightening grind onthe pointed die, as shown in FIGURE 2, is achieved by shifting the diehalf as 30 or 32 toward a generating center and re-grinding the portionof the die that will thus produce the tightening of the patch. This isshown graphically by the circular lune area indicated as t.

It is believed that it will be clearly apparent from the abovedescription and the disclosure in the drawings that the inventioncomprehends a novel Method and Means for Producing Tight-Fitting Patchesfor Use in Plywood- Patching Machines.

Having thus disclosed the invention, I claim:

1. A cutting and compressing die for veneer patching machines,comprising: a base block having a planar surface to receive veneer to bepatched and including an elliptical female cutting opening providing afemale cutting edge extending from said planar surface through said baseblock; wall means perpendicular to said planar surface forming anelliptical male cutting edge at the opposite surface of said base blockand surrounding said through cutting opening; said elliptical female andmale cutting edges being characterized by identity in length, except forworking clearance, but each said male cutter edge being enlarged between0.001" and 0.007" outward from the longitudinal axis of said ellipsesbeyond the corresponding cutter edge of the female cutting opening; theinner surfaces of said opening providing an upper wall portionperpendicular to and adjacent said planar surface; an outwardly steppedlower wall portion adjacent the male cutting edge perpendicular to saidplanar surface; and a sloping surface joining said two wall portions.

2. A cutting and compressing die for veneer patching machines,comprising: a base block having a planar surface to receive veneer to bepatched and including a through opening extending from said planarsurface through said base block; wall means forming an upper cuttingedge on the upper face of the base block and a lower cutting knife edgeat the opposite surface of said base block and surrounding said throughcutting opening; said cutting knife edge adapted to be sharpened only onits outer surface; said upper cutting edge and said lower cutting knifeedge being characterized by identity in cutting size, except for workingclearance, said lower cutting edge being enlarged between 0.001 and0.007" outward from the longitudinal axis of said die openings beyondthe corresponding upper cutting edge of the through cutting opening atthe minor axis and diminishing to zero at each end of the longitudinalaxis; the inner surfaces of said opening housing a wall portionper-pendicular to and adjacent said planar surface; an outwardly steppedwall portion adjacent the male cutting edge perpendicular to said planarsurface; and a conical surface joining said two wall portions.

3. A sequential die and operating means therefor for producingtight-fitting wood patches for patching veneer sheets used in theproduction of plywood, consisting of: a

compound die, formed of two portions joined along its major axis andeach portion having a similar circular segment cut therein, having aplanar shurface for engaging a sheet of veneer to be patched; means forholding said sheet in operational contact with said planar surface; anopening through said die at right angles to said planar surface; theupper portion of said opening formed as a vertically walled table die; ahole punch adapted to coact with said table die to cut out defects insaid veneer sheet; a male portion of said table die extending out fromthe side opposite the planar surface and terminating in a sharply rimmedcutting portion sharpened on its outer surface; said male die portionhaving an inner wall disposed at right angles to said planar surface,and an outer wall angularly disposed to said inner wall; said inner wallof the male die portion outwardly disposed from the correspondingportion of the table die inner wall by lune increments varying from amaximum at the minor axis approximately of 0.007" to 0.001"and-decreasing to each end of the die opening to approximately zero; aplug punch adapted to coact with said table die to cut a patch fromanother sheet of veneer that will be oversize for the hole cut by thetable die and hole punch by said increments; a tapering portion of thehole through said compound die connecting the parallel walls of thetable die and the inner wall of the male portion of the die; and saidplug punch adapted to force said patch up through the male die portion,the taper portion and the upper portion of the table die, thuscompressing the patch across the grain of the wood and finally seatingthe patch in the previously cut hole in the veneer.

4. A sequential cutting and compressing die having an elongated openingand operating means therefor for producing tight-fitting wood patchesfor patching veneer sheets used in the production of plywood, consistingof: a compound die, formed of two wall portions and each portion beingformed by a similar circular segment, having a planar surface forengaging a sheet of veneer to be patched; means for holding said sheetin operational contact with said planar surface; an opening through saiddie at right angles to said planar surface; the upper portion of saidopening formed as a vertically walled female die; a hole punch adaptedto coact with said female die to cut out defects in said veneer sheet; adownwardly disposed portion extending out from the side opposite theplanar surface and terminating in a sharply rimmed cutting portion; saiddownwardly extending die portion having an inner wall disposed at rightangles to said planar surface, and an outer wall angularly disposed tosaid inner wall; said inner wall of the said die portion outwardlydisposed from the corresponding portion of the female die inner wall bylune increments varying from a maximum at the minor axis of 0.001 to0.007" and decreasing to each end of the die opening to form an enlargedportion of the die; a plug punch adapted to coact with said die to cut apatch from another sheet of veneer that will be oversize for the holecut by the female die and hole punch by said lune increments; a taperingportion of the hole through said compound die connecting the parallelWalls of the female and adapted to act as a forcing cone and theoversized portions of the die; and said plug punch adapted to force saidpatch up through the oversized die portion, the taper portion and thefemale portion of the die, thus compressing the patch across the grainof the wood and finally seating the patch in the previously cut hole inthe veneer.

5. Die means for use in sequential veneer patching machines, comprising:a table die, fixedly positioned, and having a through opening; an uppercutting edge around the upper end of said opening and a hole punch dieadapted to coact with said cutting edge to cut out defects in veneersheets and leave a hole suitable for patching; a lower cutting knifeedge and a plug punch adapted to coact with said lower cutting edge tocut a patch from a separate sheet of veneer to fit said hole and toforce said patch up through said through opening and insert it in saidhole; said hole punch die having an outer wall perpendicular to the faceof said veneer and adapted to coact with said table die to produce ahole in said veneer with walls perpendicular to the face of said veneer;said lower cutting edge having the same opening length along thelongitudinal axis as said upper cutting edge and a width .007 greater atits minor axis than the upper cutting edge and decreasing towards theends of the longitudinal axis to zero; said plug punch adapted to coactwith the lower cutting edge of said table die to out said patch andforce it up through said opening in said table die, compressing saidpatch perpendicular to the grain, and seating said patch in said hole.

6. A method of producing and inserting tight-fitting patches in veneersheets comprising: (1) cutting a defective portion out of a sheet ofplywood veneer to'provide a cut-out opening having a peripheral wallperpendicular to the face of said veneer; (2) punch cutting a plywoodveneer replacement patch having a peripheral Wall perpendicular to thesurface of the patch using a cutter member having vertical interiorwalls, said patch having a Width exceeding the corresponding width ofsaid cut-out opening by an amount up to 0.007 at the cross-grain axisand decreasing to a maximum of 0.0.01" at the with grain axis; (3)forcing said replacement patch througha tapered opening into a hollowmember having vertical interior walls thesarne size as said cut-outopening to thereby laterally compress said replacement patch to reducethe width of said replacement patch to the size of said cut-out opening,and ejecting saidcut-outpatchfrom saidhollow member into said cut-outopening in said veneer.

UNITED STATES PATENTS 'Graves July .15, 1862 Allen Apr. 29, 1873Zimmerman Mar. 28, 1916 ,Alenius Oct. 10,1939 Skoog .,Dec. 14, .1943Skoog Nov. 16, 1948 Skoog v .Jan..22, .1952

'FDR'EIGN PATENTS Germany Sept. .25, 1936

6. A METHOD OF PRODUCING AND INSERTING TIGHT-FITTING PATCHES IN VENEERSHEETS COMPRISING: (1) CUTTING A DEFECTIVE PORTION OUT OF A SHEET OFPLYWOOD VERNEER TO PROVIDE A CUT-OUT OPENING HAVING A PERIPHERAL WALLPERPENDICULAR TO THE FACE OF SAID VENEER; (2) PUNCH CUTTING A PLYWOODVENEER REPLACEMENT PATCH HAVING A PERIPHERAL WALL PERPENDICULAR TO THESURFACE OF THE PATCH USING A CUTTER MEMBERHAVING VERTICAL INTERIORWALLS, SAID PATCH HAVING A WIDTH EXCEEDING THE CORRESPONDING WIDTH OFSAID CUT-OUT OPENING BY AN AMOUNT UP TO 0.007" AT THE CROSS-GRAIN AXISAND DECREASING TO A MAXIMUM OF 0.001" AT THE WITH-GRAIN AXIS; (3)FORCING SAID REPLACEMENT PATCH THROUGH A TAPERED OPENING INTO A HOLLOWMEMBERHAVING VERTICAL INTERIOR WALLS THE SAME SIZE AS SAID CUT-OUTOPENING TO THEREBY LATERALLY COMPRESS SAID REPLACEMENT PATCH TO REDUCETHE WIDTH OF SAID REPLACEMENT PATCH TO THE SIZE OF SAID CUT-OUT OPENING,AND EJECTING SAID CUT-OUT PATCH FROM SAID HOLLOW MEMBER INTO SAIDCUT-OUT OPENING IN SAID VENEER.